The present invention relates to the field of contour gages, and more particularly to a gage that accurately and automatically measures internal and external dimensions of hemispherical parts, both convex and concave.
In the art of measuring the surface contours of machined parts, the prior art is very limited in its disclosure of on-machine gages that permit contour measurements of machined parts while they are still on the machining equipment. Industry generally separates the task of production and inspection, wherein they are performed by two different departments in two different environments.
Among the limited prior art gaging devices that are used to measure the surfaces of machined parts while still on the machine tool, some gaging devices employ touch probes that are used in place of the cutting tool. Such touch probes use the slides on the machine tool and are limited to a point-to-point contact probing mode of operation. Consequently, such touch probe gages cannot perform any scanning action on the machined contour It would be desirable, however, if a contour gage were available that did not use the slides of the machine tool and that performed a scanning action on the machined contour.
There are gages which are known which utilize two linear Cartesian motions (e.g. an X and Y) to gage circular surfaces with a probe. With such a Cartesian driven probe, the angle between the probe and the surface is constantly changing and is other than normal to the surface, except when the angle between the X and Y motions is 45 degrees. With the Cartesian driven probe, there may be heavy side loads exerted on the probe by the surface that is being gaged. Side loads being exerted on the probe can be the cause of erroneous data with respect to the gaged surface. It would be desirable to have a probe system which constantly maintains the probe normal to the surface being gaged thereby avoiding side loads being exerted on the probe.
Another problem associated with contour gages that employ Cartesian motions is that the gage probes directly contact the surface being measured. The direct contact is undesirable because of the frictional drag between the probe and the surface. The direct contact is also undesirable because there is the possibility that extraneous particles may be trapped between the probe and the surface bringing out an erroneous reading and causing damage to the probe. It would be desirable, therefore, to be able to measure the contour of a surface using a probe that does not directly contact the surface being measured.
In the prior art, fluid probes, also known as pneumatic probes, are known for measuring overall surface characteristics. For example, U.S. Pat. No. 4,325,248 of Kolosov discloses that the thickness of a storage cell plate is measured by an indirect measurement in which a pressure change in a pneumatic probe is used to dislocate a diaphragm, and the movement of the diaphragm disrupts a light path leading to a photo-electric transducer. The details of the contour of the surface of the plate are not scanned, and the thickness is obtained by integrating the entire surface of the plate. In view of the complexities in the measurement system of the Kolosov patent involving a photo-electric transducer, and in view of the lack of scanning of the surface of the plate, it would be desirable to have a fluid probe system that does not use a photo-electric transducer. It would also be desirable to have a fluid probe system in which the surface contour is scanned to provide detailed surface contour information rather than merely an integrated value for the entire surface.